Regenerative turbine pumps are one of many types of pumps that have the capability to deliver fluid from one location to another. Typically, a pump transfers energy into a fluid flow system in order to overcome some differential pressure, moving fluid in the system from lower pressure to higher pressure. Normally, regenerative turbine pumps add energy to the system by adding centrifugal force and shearing action to the fluid.
Regenerative turbine pumps close a void between centrifugal and positive displacement pumps. Generally, a regenerative turbine pump includes an impeller that has a multiplicity of impeller vanes in series. In a regenerative turbine pump, fluid travels in a unique circulatory flow pattern through vanes of the impeller. Fluid travels in multiple cycles through several vanes of a turbine impeller, whereas fluid only passes once through a centrifugal impeller. Preferably, turbine impeller vanes impart a centrifugal force outward toward the impeller periphery, which pushes the fluid into a circulatory flow pattern. The circulatory flow patterns of fluid within the impeller vanes may be accurately compared to a helical spring, where opposite ends of the spring are bent in a circle around a given axle until they connect. Under such a description, a pump operation under low head would yield increasing space between the helical coils, whereas a pump operation under high head would yield decreasing space between the helical coils. The circulatory flow within the impeller vanes occurs while the entire impeller revolves in an annular channel. Recirculation of liquid among the vanes of a turbine impeller occurs several times between suction and discharge. As the fluid repeatedly circulates, the flow inside of the vanes generates increasing fluid velocity. The kinetic energy associated with the fluid velocity may be utilized to increase the flow velocity and/or pressure of the fluid. Multiple cycles of fluid recirculation in the impeller vanes to build fluid velocity is known as “regeneration.”
Many times, regenerative turbine pumps are used in applications that have high head pressure and low fluid flow characteristics. Generally, in situations with very high head pressure and low fluid flow, the pump is susceptible to leakage. Therefore, very tight internal tolerances are typically required between the impeller and raceway to reduce the leakage within the pump.
Some regenerative turbine pumps do not have any adjustable features used in parallel with a selected-fit between the impeller and a fixed raceway to achieve and maintain the tight tolerances required for adequate performance of the pump. Generally, the raceway navigates fluid into the impeller and provides a channel, through which liquid travels as it is propelled by the impeller. However, after use in the field, the impeller, the raceway, and/or the sealing means used to between them may gradually wear due to frictional fluid flow, causing the clearance between the impeller and the raceway to increase. Consequently, pump performance would suffer and in order to regain optimal performance characteristics, the instrument would require costly and time-consuming adjustments of the pump clearances.
The known prior art lacks a pump that does not require a select fit between the raceway and the impeller; a pump that can automatically compensate for wear; and a pump that does not require field adjustment of the pump clearances after installation to maintain desired tolerances between the impeller and raceway. Accordingly, a pump is desired which provides an inexpensive means to eliminate the costly selected fit of the impeller with the raceway. Furthermore, it is desired to provide a pump which is self-adjusting to maintain a constant state of compliance.